The present invention relates to closable and reopenable plastic containers, and, more particularly, to such containers having a separate cup and lid which, when attached to close the container, provide a continuous seal and locked engagement, but having manually engageable tabs on the lid to facilitate relative rotational movement between the two for opening.
U.S. Pat. No. 6,688,487 describes a sealed, locked and reopenable cup and lid assembly utilizing a cup that has an open circular mouth defined by an upper edge, a radially inwardly opening locking groove below the upper edge, and a resilient circular lid that is sized to be inserted into the open mouth of the cup and which has an outer peripheral lip that is received with a snap fit in the locking groove in the cup. The locking groove and the peripheral lip include interrupted portions that are circumferentially spaced and rotationally alignable to permit removal of the lid.
The foregoing prior art cup and lid are also provided, respectively, with a frustoconical inner wall portion that extends downwardly and diverges outwardly from the locking groove and a frustoconical sealing wall that extends downwardly and diverges outwardly from the peripheral lip. The frustoconical inner wall portion of the cup is engaged by the frustoconical sealing wall of the lid as the lid is snapped into the locking groove to provide a liquid-tight seal.
When applying the foregoing technology to non-liquid or non-beverage containers, a number of problems have been encountered. First of all, the larger diameter of some containers, such as may be used at point-of-sale or for home storage and reuse, make it difficult for the user to grip the container body and rotate the lid to align the interrupted portions in the locking groove and lip to permit reopening. In addition, the liquid tight seal provided by engagement between the frustoconical inner wall of the cup and the frustoconical sealing wall of the lid may be so tight as to inhibit relative rotational movement between the lid and cup when grasped by the user. Furthermore, when the container and lid are used for dry or semi-solid storage, a dust-tight seal may be adequate and a liquid-tight seal is not necessary.